Automatic circuit-controlling device



A i-1'19, 1929. .1. A. JACKSON 1,708,886

' I I AUTOMATIC CIRCUIT CONTROLLING DEVICE Filed Aug. 26, 1925Inventor-z James A. Jackson, by M12 His Attorney Patented Apr. 9, 1929.

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JAMES A. JACKSON, OF SCI-IENEO TADY, NEW YORK, ASSIGEJOP, T0 GENERALELECTRIC COMPANY, A CORPORATION 05' NEVI 1 03K.

AUTOI'IIATIC CIRCUIT-CONTROLLING DEVICE.

Application filed August 26, 1925. Serial No. 52,662.

This invention relates to automatic controlling devices for electriccircuits adapted to be energized troma plurality of sources 'ofditleringvoltages, andit has for its object the provision oif automaticelectroresponsive switch mechanism for disconnecting the controlledcircuit from a high voltage source and connectingthe circuit to a lowervoltage source when the current in the circuit exceeds a certain valueand for automatically reconnecting the circuit to the higher voltagesource when the current decreases below the predetermined value.

Although of general application to power circuits, motor circuits, andthe like, the invention is particularly advantageous when applied tocontrol the energization of the train power conductors f in an automaticelectric railway system of the type described and claimed in theco-pending patent application of Robert H. McLain, No. 751,228, filedNovember 21, 1924, and assigned to the assignee of my present invention.In the McLain type of automatic railway electric system the cars aredriven by alternating current motors and are arranged to be operatedupon a main track which is normally energized from an alternating onrent source of relatively high constant frequency without operators ormotormen thereon.

hen applied to such an automatic, electric railway system, my presentinvention provides an automatic circuit controlling device capable ofrestarting trains. of motor driven cars which may be stopped on the maintrack upon failure of the source normally energizing the same withoutexcessively overloading the source or excessively overheating thedriving motors of the cars. This is accomplished in accordance with myinvention entirely automatically by means of switch mechanism arrangedto transfer the energization of the train conductors from the highvoltage source to a low voltage source when the starting andaccelerating current of the stalled trains oi? cars onceeds a certainvalue, and to reconnect the train conductors to the high voltage sourceafter the motor starting current has decreased to the normal runningvalue.

In the accompanying drawing the inven tion is illustrated as applied tosuch an autovniatic electric railwa system in order to explain theprinciples thereof, although it will be understood that the inventionmay be used in other connections. The single figure of the drawingdiagrammatically shows a preferred form of automatic electroresponsiveswitch mechanism for transferring the energization of the train powerconductors in an electricrailway system between a high voltage sourceand a low voltage source responsively to the current in the trainconductors.

In the drawing the train power conductors comprising the track T and thetrolley T are arranged to receive power from the high voltagealternating current supply line L through the. transformer 10, having aprimary winding 11 and a tapped secondary winding 12. One terminal ofthe secondary winding .12 is permanently connected to the track T Theelectromagnetic switch 13 controls the connection of the high voltageterminal 14 of the secondary winding 12 to the trolley wire T while theelectromag netic switch15 controls the connection of the intermediatelow voltage tap or terminal 16 of the secondary winding 12 to thetrolley wire T Eachof the electromagnetic switches 13 and 15 is biasedto the open position. The electroresponsive relay 17 is provided with anormally closed contact 18 and a normally open contact. 19 forcontrolling the energization of the operating windings of the respectiveelectromagnetic switches 13 and 15. v

The relay 17 is provided with a pair of windings 21 and 22, theformerofwhich is connected in the circuit through which the trolley wire T isenergized from the high voltage terminal 1a of the secondary winding 12,while'the latter is connected in the circuitthrough which the trolleywire T is energized from the low voltage tap .16 of the secondarywinding 12.

When the supply lines L are energized and trains of cars are operatingupon the track T under normaloperating conditions relay 17 is in theposition in which it is shown and the operating winding ofelectrolnagnetic'switch 13 is energized through the normally closedrelay contact 18. Thus the electromagnetic switch 13 is closed toconnect the trolley wire Cl to the high volt-- age terminal 14 oi. thesecondary winding 12. The normal operating current supplied to thedriving motors of the cars from the high voltage terminal 14 through thewinding 21 of relay 17 is insufficient to operate the relay from theposition in which it is shown.

In case of failure of the source supplying power to the supply lines Lthe driving motors of the cars operating upon. the track T aredeenergized and hence the cars slow down and come to rest. Also theoperating winding of electromagnetic switch 13 is deenergized and theswitch operates to the open position. Upon the return of power to thesupply lines L the electromagnetic switch 13 is reenergized andreconnects the trolley wire T to the high voltage terminal 14 of thesecondary winding 12 to apply full voltage to the driving motors of thestalled train of cars. Under these conditions the starting current ofthe motor increases to abnormally high values, for example, from 300 to400% of normal running current. The excessive value of current throughthe operating winding 21 of relay 17 serves to operate the relay to openthe contact 18 and close the contact 19. Upon the resultingdeenergization of the electromagnetic switch 13, the switch opens inaccordance with its bias. Upon the closure of contact 19 the operatingwinding of electromagnetic switch 15 is energized through a circuitextending from the terminal of secondary winding 12 connected to track Tthrough the contact 19, the operating winding of switch 15, and theoperating winding 21 of relay 17, to the high voltage terminal 14 of thesecondary winding 12. Switch 15 at once closes and connects the trolleywire T to the low volttage tap 16 of the secondary winding 12 throughthe operating winding 22 of relay 17. The reduced voltage now applied tothe driving motors of the cars upon track T maintains the starting andaccelerating current within sate operating limits, for example, 200% ofnormal running current. The driving motors gradually accelerate the carsto normal running speed. During this interval the current taken by themotors from the low voltage tap 16 gradually decreases. lV hen thecurrent in the train conductors T and T decreases bQlOv' a certainvalue, for example, 125% normal running value, the operating winding 22of relay 17 is insufiiciently energized to maintain the contact 19 inthe closed position. Upon the resulting opening of contact 19,electromagnetic switch 15 is deenergized and opens to disconnect thetrolley wire T. from the low voltage tap 16. At the same time thecontact 18 reestablishes the energizing circuit for electromagneticswitch 13. This switch then closes to reconnect the trolley T to thehigh voltage terminal 14 of the secondary winding 12 for normal runningoperation of the cars.

Thus it will be seen that by means oi my invention the train conductorsT, and T are normally energized from the high voltage terminal 14 aslong as the current in the control circuit is below a predeterminedvalue, while the energization of the track conductors T and T is shiftedfrom the high voltage 14 to the low voltage tap 16 and maintainedconnected to the latter as long as the current of the track conductorsexceeds a certain value.

While I have described the invention in connection with a power circuitfor electric railways adapted to be energized from a high and a lowvoltage source, the invention may be applied with equal advantage to thecontrol of other circuits.

lVhat I claim as new and desire to secure by Letters Patent of theUnited States is 1. An automatic controlling device for electriccircuits adapted to be energized from a high voltage source and from alow voltage source comprising electrically operated switch mechanism forseparately connecting the controlled circuit to each source, anelectroresponsive relay having a pair of operating windings, eachconnected under the control of said switch mechanism to be energizedresponsively to the current supplied to the circuit from a correspondingone of said sources and arranged to be operated to one position when thecurrent in the controlled circuit is below a predetermined value and toa second position when the current in the circuit is above saidpredetermined value, and connections controlled by said relay in saidone position for effecting operation of said switch mechanism to connectthe controlled circuit to the high voltage source and .in said secondposition for ellecting operation of said switch mechanism to connect thecontrolled circuit to the low voltage source.

2. The combination of an electric circuit, a transformer having a highvoltage and a low voltage terminal for supplying power to said circuit,a separately operable electromagnetic switch for connecting each of thesaid terminals to the circuit, and an electroresponsive relay having apair of operating windings, one connected under the control of one ofsaid switches to be energized by the current supplied to said circuitfrom the high voltage terminal of the transformer and the otherconnected under the control of the other of said switches to beenergized by the current supplied to said circuit from the lowvoltageterminal of the transformer, said relay being biased to one positionwhen the current supplied to the circuit from either terminal of thetransformer is below a predetermined value and arranged to operate to asecond position When the current supplied to the circuit exceeds saidValue, and connections controlled by said relay in said one position fornormally energizing the first electromagnetic switch to connect theelectric circuit to the high Voltage ter- Ininal and in said secondposition to energize said second contactor to connect the electriccircuit to the low Voltage terminal.

In Witness whereof I have hereunto set my hand this 25th day of August,1925.

JAMES A. JACKSON.

